Hello Tina, You might try taking Mucinex starting at least 24 hrs before. And use a PEP such as Aerobika before you nebulize with 7% saline, then do some exercise that gets your respirations elevated, then lay on a flat surface and get someone to do some manual chest percussions, then while still lying down do a series of Huff coughing, then finally sit up and do some regular coughing hopefully bringing up enough sputum for your culture. Good luck, Bill